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Thu, 27 Aug 2026 23:42:22 -0700 (PDT) From: Dmitriy Okunev To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , Sasha Levin , lvc-project@linuxtesting.org, Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrey Gusakov , Philipp Zabel , Archit Taneja , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH] drm/bridge: tc358767: prevent overflow in PLL calculation Date: Fri, 28 Aug 2026 09:42:09 +0300 Message-ID: <20260828064209.4314-1-dokunevdmitriy@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In the tc_pxl_pll_calc() function, the expression `pixelclock * ext_div[i_pre] * ext_div[i_post] * div` is calculated using 32‑bit arithmetic, since all operands are of type u32 or int. pixelclock takes the maximum value of 154 MHz (in accordance with tc_edp_mode_valid()), ext_div[...] takes the value 7, and div ranges from 1 to 16, inclusive. The maximum product (154,000,000 * 7 * 7 * 16) is approximately 1.2e11, which is much larger than UINT32_MAX, leading to an overflow and, as a result, to an incorrect value of the PLL multiplier. Fix this by casting `pixelclock` to `u64` before the multiplication, ensuring all arithmetic is performed in 64-bit precision. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: 7caff0fc4296 ("drm/bridge: tc358767: Add DPI to eDP bridge driver") Signed-off-by: Dmitriy Okunev --- drivers/gpu/drm/bridge/tc358767.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c index e3a57f8228da..39633f618664 100644 --- a/drivers/gpu/drm/bridge/tc358767.c +++ b/drivers/gpu/drm/bridge/tc358767.c @@ -640,7 +640,7 @@ static int tc_pxl_pll_calc(struct tc_data *tc, u32 refclk, u32 pixelclock, if (iclk < 6000000 || iclk > 40000000) continue; - tmp = pixelclock * ext_div[i_pre] * + tmp = (u64)pixelclock * ext_div[i_pre] * ext_div[i_post] * div; do_div(tmp, refclk); mul = tmp; -- 2.53.0